Dehydration of organic materials is commonly done in the food processing industry and in the production of biologically-active materials, to preserve the products for storage, to concentrate non-volatile components, or to create a product that is used in the dehydrated form, for example dried herbs and various kinds of chips. It is known to dehydrate food products and biologically-active materials by microwave vacuum dehydration. Examples of this in the patent literature include WO 2009/049409 A1, Durance et al., published Apr. 23, 2009, and WO 2009/033285 A1, Durance et al., published Mar. 19, 2009. Microwave vacuum-drying is a rapid method that can yield products with improved quality compared to air-dried and freeze-dried products. Because the drying is done under reduced pressure, the boiling point of water and the oxygen content of the atmosphere are lowered, so food and medicinal components sensitive to oxidation and thermal degradation can be retained to a higher degree than by air-drying. The drying process is also much faster than air- and freeze-drying. The present invention is directed to improvements in the art of microwave vacuum-drying.